From the Chicago Manual of Style blog. CMOS Shop Talk::  "The 18th edition will retain much of the core advice from the 17th while addressing an array of developments that directly affect how writers, editors, and publishers do their work." 

We'll be adding these changes to our citation examples but in the meantime, here are some highlights: 

• A city or other place of publication will no longer be required when citing books
• In titles of works, prepositions of five or more letters will now be capitalized (A Room with a View but Much Ado About Nothing).
• An initial The in the title of a newspaper or other periodical that includes one (as on a masthead or cover) will now be retained in running text (The New York Times and The American Naturalist but the Chicago Tribune and the American Journal of Sociology).
• The terms ebook and esports will join email as exceptions to the rule for hyphenating e-terms.
• The generic singular they will now be considered acceptable even in formal writing—for example, when the antecedent is an indefinite pronoun (someone forgot their coat) or when referring to a person whose gender is unknown or irrelevant (will the driver of the yellow sedan please move their car) or whose identity must be concealed (the author wants their privacy protected). These generic uses complement the referential singular they, which we covered for the first time in the last edition relative to people who identify with they/them pronouns.
• A new section covers Indigenous languages and sources while guidance on accessibility and inclusive language have been revised. 

-CMOS Shop Talk, April 16, 2024. 

The Chicago Manual of Style  provides extensive instructions for two different citation systems:

Chicago Notes and Bibliography style (sometimes called "Chicago A") uses footnotes or endnotes supplemented by a concluding bibliography. This style is commonly used by scholars in the fields of history and the humanities. This format is discussed at length in chapter 14 of the Manual.

Chicago Author/Date style (sometimes called "Chicago B") uses parenthetical or in-text references containing author last name and date of publication, with full bibliographical detail given in a concluding reference list. This style is used more often in the sciences, and is discussed at length in chapter 15 of the Manual.

Kate Turabian's A Manual for Writers of Term Papers, Theses, and Dissertations provides a simplified guide to using Chicago style for students.